bum

1. To make highly efficient, either in time or space, often at
the expense of clarity. "I managed to bum three more
instructions out of that code." "I spent half the night
bumming the interrupt code." In elder days, John McCarthy
(inventor of Lisp) used to compare some efficiency-obsessed
hackers among his students to "ski bums"; thus, optimisation
became "program bumming", and eventually just "bumming".

2. To squeeze out excess; to remove something in order to
improve whatever it was removed from (without changing
function; this distinguishes the process from a
featurectomy).

3. A small change to an algorithm, program, or hardware
device to make it more efficient. "This hardware bum makes
the jump instruction faster."

Usage: now uncommon, largely superseded by v. tune (and
tweak, hack), though none of these exactly capture sense
2. All these uses are rare in Commonwealth hackish, because
in the parent dialects of English "bum" is a rude synonym for
"buttocks".